7.3. Map Files, GRUB, and LILO

The main obstacle for booting an operating system is that the kernel
is usually a file within a file system on a partition on a disk. These
concepts are unknown to the BIOS. To circumvent this,
maps and map files were
introduced. These maps simply note the physical block numbers on the disk
that comprise the logical files. When such a map is processed, the BIOS
loads all the physical blocks in sequence as noted in the map, building the
logical file in memory.

In contrast to LILO, which relies entirely on maps, GRUB
tries to gain independence from the fixed maps at an
early stage. GRUB achieves this by means of the file
system code, which enables access to files by way of the
path specification instead of the block numbers.

Boot Loader Selection

If you update from a previous version of SUSE LINUX in which LILO was the
boot manager, the new system continues to use LILO. If you install
SUSE LINUX from scratch, the system uses GRUB unless the root
partition is installed on a RAID system of the following types:

CPU-controlled RAID controllers, such as many Promise and Highpoint
controllers